碳化泥质板岩大断面隧道围岩松动圈测试研究

围岩松动圈范围是隧道、巷道及类似地下工程设计、施工和评价围岩稳定性的重要技术参数之一。针对吉图珲高速铁路小盘岭大断面碳化泥质板岩隧道在掘进过程中发生的地层变形大、频繁更换钢拱架以及隧道局部多次发生垮塌这一严重现象,采取多点位移计监测及超声波检测技术,对小盘岭隧道围岩松动圈范围进行测试。在此基础上,通过改变围岩壁后注浆深度,对比分析控制效果。现场测试表明,小盘岭隧道围岩松动范围大,平均达到约5 m,隧道开挖右侧松动圈范围大于左侧松动圈范围,原支护方案中锚杆长度仅为4.0 m,径向注浆管长度为3 m,初步判断施工步距大以及锚杆长度过短是造成隧道围岩失稳的重要因素。在后续的施工过程中,采取右侧及拱顶锚杆长度为6.5 m,左侧锚杆长度为6 m,围岩径向注浆管长度增加到5 m,经过优化后的锚杆长度参数明显改善了围岩的支护效果,监测表明隧道拱顶沉降及围岩收敛速率明显减小,拱架受力明显降低,降低了隧道施工风险,并为类似工程的设计及施工提供参考。

Expenimental Research on Surrounding Rock Loose Circle of Carbide Argillaceous Slate Large Cross Section Tunnel

The surrounding rock loose circle area is one of the important technical parameters of surrounding rock stability of tunnel, underground engineering design, construction and evaluation. For Ji-Tu-Hun high-speed railway Xiao Pan-ling large section carbonization argillite tunnel, phenomenon of large deformation in tunneling process, frequent replacement of steel arch and part of tunnel collapse occurs several times. Taking the multi-point displacement meter monitoring and ultrasonic detection technology, tests were conducted on the surrounding rock loose circle range Xiao Pan-ling tunnel. On this basis, through changing surrounding rock wall back grouting depth, comparative analysis of the control effect was made. Field tests show that, the surrounding rock loose circle Xiao of Pan-ling tunnel is large, to achieve an average of about 5 m, the loosen range on the right side is greater than left loose circle, bolt length is only 4.0 m in the original support scheme, radial grouting pipe length is 3 m. Preliminary judge that large construction step and anchor length too short are important reason for tunnel surrounding rock instability failure. In the follow-up construction process, a right and crown bolt length is 6.5 m, left rock bolt is 6 m in length, radial grouting pipe length increases to 5 m. After optimization, surrounding rock supporting effect was significantly improved. Monitoring shows that the tunnel vault subsidence and surrounding rock convergence rate was significantly reduced, arch stress reduction, reducing the risk of tunnel construction, and it can provide a reference for the design and construction of similar projects.